In internal combustion engines, the bearing assemblies typically each comprise a pair of half-bearings retaining a crankshaft that is rotatable about an axis. For crankshaft journal bearing assemblies, at least one half-bearing may be a flanged half-bearing that comprises a hollow, generally semi-cylindrical, half-shell bearing provided with a generally semi-annular thrust washer extending outwardly (radially) at each axial end.
OEMs in the automotive sector, including engine and subassembly manufacturers, typically specify that an assembled flanged bearing is supplied as part of the main bearing set. This allows for ease of installation and keeps the thrust washer in place during the life of the engine. The assembled flanged bearing is expected to be rigid enough to cope with transportation and handling by operators and/or robots and to be flexible enough to accommodate machining tolerances in the engine and to permit installation, e.g. into the designated space in an engine block. The flanged bearing is typically required to be provided with some means for supporting torque loads of the engine without the thrust washers becoming detached and to oppose rotation of the thrust washers relative to the half-shell bearing.
In some known flanged half-bearings, a single-piece construction of the half-shell bearing and thrust washers is used.
In other known flanged half-bearings, such as the one described in published US patent application number US2005223546, the half-shell bearing and the thrust washer are permanently assembled using by a joining process such as laser welding. Disadvantages of this type of arrangement include that the weld spot can break and the debris can pass into the clearance space between the journal and bearing and that the resulting assembly can be very stiff, affecting the ease with which it can be installed into an engine block.
In a further type of flanged half-bearings, the thrust washers are permanently assembled onto the half-shell bearing by deformation of corresponding engagement features.
With reference to FIGS. 1-4, other known features for mechanically engaging a thrust washer around the outer surface of a half-shell bearing, at an axial end, include a generally semi-annular panel with a pair of hooking lugs (or tongs) projecting inwardly from the semi-circular inner edge. The hooking lugs hook into corresponding openings in the half-shell bearing when the thrust washer is connected around the outer surface at an axial end of the half-shell bearing. The inwardly projecting hooking lugs are located to either side of the crown of the bearing, towards the joint faces, and are shaped to enable the thrust washer to be assembled onto the half-shell bearing when the half-shell bearing is resiliently or elastically deformed by pinching together the joint faces (circumferential end faces). The arrangement by which the hooking lugs engage with the openings (recesses) prevents separation once the half-shell bearing has returned to the relaxed position, and also prevents separation when the half-shell bearing has been slightly pinched together through being held in an interference fit with a housing, within the full bearing assembly. The hooking lugs typically have a uniform thickness and are machined to be thinner than the main semi-annular panel of the thrust washer, to enable the use of (axially) narrow openings in the half-shell bearing. One or more stabilisation lugs may be provided intermediate the hooking lugs, projecting inwardly from the inner edge of the semi-annular main panel, to reinforce the connection between the thrust washer and half-shell bearing, to prevent wear leading to substantial relative rotation of the thrust washer and half-shell bearing.
The prior art includes U.S. Pat. No. 4,533,261 and European patent number EP2233759 which provide flanged half-bearings in which thrust washers are loosely mechanically engaged with half-shell bearings using thin hooking lugs of uniform thickness that are receivable within openings in a corresponding half-shell bearing.
The prior art also includes PCT publication number WO2013/068106 which provides a flanged half-bearing (330) comprising at least one substantially semi-annular thrust washer (100A, 100B) with an internal periphery having lateral lugs (104A, 104B) and an Intermediary stabilisation lug (106) projecting from the Internal periphery (108) of the thrust washer, and a semi-cylindrical half journal half-shell bearing (220) having lateral recesses (226A, 226B) and an intermediary stabilisation recess (228) that are recessed into an axial end face (224A, 224B) of the half-shell bearing and are respectively connected to the lateral lugs and the stabilisation lug of the thrust washer, wherein the stabilisation lug (106) has rotational stabilisation edges (114) that project substantially perpendicularly from the inner periphery (108) of the thrust washer, and the stabilisation recess (228) is configured for axial relative movement of stabilisation lug; and an engine comprising at least one such flanged half-bearing (330).
The prior art also includes PCT publication number WO2015/007826 which provides a thrust washer (100) for a flanged half-bearing, the thrust washer comprising: a substantially semi-annular panel (102) having an inner edge (108) and outer edge; and hooking lugs (110) projecting inwardly from the inner edge of the panel, wherein the hooking lugs have latching edges (118) that are configured to engage within corresponding openings in a half-shell bearing received by the thrust washer and to prevent disconnection of the thrust washer and half-shell bearing without deformation of the half-shell bearing, each hooking lug has a hooking lug inner portion (104A) proximate, around the inner edge of the panel, to the central part of the thrust washer for engaging against edges of the openings in the half-shell bearing and a hooking lug outer portion (104B) remote, around the inner edge of the panel, from the central part of the thrust washer, and the hooking lug inner portion is thinner than the hooking lug outer portion.
The inventors have appreciated that there may be a number of limitations or disadvantages associated with known types of flanged half-bearings such as those described in the aforementioned prior art references and illustrated in FIGS. 1 to 4. These may comprise one or more of the following, among others:                i. shown in FIGS. 1 to 4, the prior art flanged half-bearings 1 use clips or ‘tangs’ 2,3,4,5 proximate the ends of the thrust washers 6,7 for engagement with corresponding notches or recesses 8,9,10,11 proximate the ends of the half-shell bearing 12. These tangs are typically the only thing which hold the thrust washers in engagement with the half-shell bearing. It may be fiddly to engage the tangs with the corresponding notches or recesses which may necessitate manual handling of the thrust washers and the half-shell bearing;        ii. the tangs of the prior art devices may require the ends of the half-shell bearing to be pinched to permit engagement of clips or ‘tangs’ with corresponding notches or recesses;        iii. formation of the close tolerance tangs and corresponding notches of the prior art devices may lead to an increase in the manufacturing lead time;        iv. the tangs of the prior art devices may lead to scrappage of a higher proportion of assembled flanged half-bearings than may be desirable due to the thrust washers not being correctly fitted to the half-shell bearing or becoming detached from the half-shell bearing during transportation and handling;        v. the tangs and the corresponding notches or recesses of the prior art being the only thing that forms a self-supporting flanged half-bearing necessitates the use of close tolerances between the tangs and the corresponding notches or recesses. This may require the use of certain manufacturing processes and rigid quality controls;        vi. the need for close tolerances may also necessitate the use of post-processing operations, such as deburring or the removal of ledges on the tangs and/or the corresponding notches or recesses which may result from the initial forming operation, or the machining of one or more chamfers to facilitate engagement of the tangs and the corresponding notches or recesses. This has the potential to introduce debris (e.g. swarf or metal particulate) which may have an adverse impact on the performance of the half-shell bearing and/or the thrust washers;        vii. the need for additional post-processing operations may add to the cost of manufacture and may have an impact on the manufacturing lead time. It may also contribute to a higher proportion of the thrust washers and/or half-shell bearings being scrapped than may be desirable due to errors in the post-processing operations;        viii. the tangs of the prior art devices, may lead to the resulting flanged half-bearing assembly having greater stiffness, or lower flexibility, than may be desirable for simple and effective installation of the flanged half-bearing into a recess in an engine housing;        ix. the use in some prior art devices of lines or runs of tack welding to permanently join the thrust washers and the half half-shell bearing may necessitate the use of jigs to support each assembly during manufacture. The resulting flanged half-bearing may also be relatively stiff and have low flexibility which may be undesirable for simple and effective installation of the flanged half-bearing into the end product, for example an engine housing; and        x. the use of welding also has the potential to introduce impurities and/or debris (e.g. weld dust) which may have an adverse impact on the performance of the half-shell bearing and/or the thrust washers.        